The research deals with the clinical efficacy of LAAM (Acetyl Methadyl) as a maintenance drug in heroin addiction and with the safety of the drug. The research has two parts: 1. Continuation of the cooperative SAODAP LAAM Study from 40 to 80 weeks. 2. Analysis of existing data collected by the University of Chicago and the Illinois Drug Abuse Program. This analysis will have four objectives: 1. To codify the data in a uniform manner, consistent with the SAODAP LAAM data collection forms. 2. To compare the results from open and blind LAAM-methadone studies. 3. To perform follow-up analyses for previous subjects who remained in treatment in the Illinois Drug Abuse Program. Variables such as dosage, drug use and retention will be examined. 4. To re-analyze the data in an attempt to discover if differential reasons for dropping out exist for LAAM and methadone patients. 3. To include females of proven non-childbearing potential in the sample.